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Introduction to Amino Acids Overview

Educational Guide

Introduction to Amino Acids

What are Amino Acids?

Amino acids are organic compounds that contain both an amino group (-NH2) and a carboxyl group (-COOH). They are the building blocks of proteins.

  • Biochemistry
  • Proteins
  • LifeScience

Amino acids are the basic building blocks of proteins and are essential for many vital functions in the human body.

Side Chain (R Group)

Variable group that gives each amino acid its unique properties

Carboxyl Group (-COOH)

Acidic group

Hydrogen (H)

Central atom bond

General Formula

H2N - CH(R) - COOH

Amino Group (-NH2)

Basic group

Functions & Physiological Importance

  1. 1Tissue Repair & GrowthBuild and repair body tissues (e.g., muscles, skin, organs).
  2. 2Proteins & EnzymesForm proteins and enzymes essential for biological catalysis.
  3. 3Hormones & NeurotransmittersHelp in the production of hormones, neurotransmitters, and other important molecules.
  4. 4Nitrogen Balance & PrecursorsMaintain nitrogen balance in the body and serve as precursors for other biomolecules (e.g., glucose, creatine, heme).

Classification of Amino Acids

  1. 1Based on Side Chain (R Group)Divided into nonpolar (hydrophobic) and polar (hydrophilic) based on the nature of their side chain.
  2. 2Based on Charge at Physiological pH (~7.4)Amino acids can be acidic (negative charge), basic (positive charge), or neutral depending on the charge of their side chain at pH 7.4.
  3. 3Based on Nutritional RequirementDivided into essential (must be obtained from diet) and non-essential (can be synthesized by the body).
  4. 4Based on Structural FeaturesGrouped into aliphatic amino acids (straight or branched hydrocarbon chains) and aromatic amino acids (aromatic ring in side chain).

Nomenclature of Amino Acids

  1. 1Common (Trivial) NameUsed for most amino acids, based on the source from which they were first isolated. Usually end with -ine (except glycine). Examples: alanine, glycine, serine, leucine, phenylalanine.
  2. 2Systematic (IUPAC) NameBased on IUPAC rules of organic chemistry. Formed by replacing the ending -ic acid of the parent carboxylic acid with -amino. Examples: 2-aminopropanoic acid, 2-aminoacetic acid.
  3. 3AbbreviationsUsed in scientific writing and biochemical literature. Consist of 3 letters or 1 letter for some (e.g., Alanine -> Ala, A; Glycine -> Gly, G).

Quantitative Tests for Amino Acids (For BS MLT Students)

Biuret Test

Blue -> Purple

Reagents: Copper sulfate + Sodium Hydroxide (NaOH). Detects proteins in serum and urine samples to assess protein levels.

Ninhydrin Test

Yellow -> Deep Purple

Reagents: Ninhydrin solution. Identifies free amino acids in urine, used in aminoaciduria screening.

Xanthoproteic Test

Yellow -> Orange

Reagents: Concentrated Nitric Acid (HNO3) + Heat. Detects aromatic amino acids like tyrosine and tryptophan in proteins.